My initial reaction is haven't the men done enough to this poor woman?
She was born in 1477 and only married Louis XII because he was able to get an annulment from Pope Alexander IV. She was contractually (by the marital contract with second husband Charles VIII - she'd been legally wed to Maximilian before him) to wed Charles' successor (Louis, who claimed his wife was sterile and the Pope went along with it). By this time in her life she's had seven or so pregnancies with Charles and eight or nine with Louis. And what does she have to show for 15 or 16 pregnancies? Two girls. She's also 34/35 and going to start menopause soon. I seriously doubt that the amorous Francis wants to be fourth in line. Claude will inherit Brittany, he doesn't have to wed her mother to get it (the reason Louis wanted to wed her). Francis will still wed Claude.
Besides, she didn't want to marry Louis. I'm sure she's tired of being pregnant and she can retire with dignity and will jump at the chance to go to Brittany and run things there.
So, to answer your questions with my opinion (which is, like everyone else's, questionable): If Francis married Anne, Claude will wed the next guy in line while Renee (who's like two years old) will still go to the Duke of Ferrera as "payment" for the annulment. (D'Este is a son-in-law of Pope Alexander IV). I doubt Francis would be dumb enough (and even if he is, his mother isn't) to wed both daughters of Louis XII to heirs direct. (It's rumored Francis' mum used witchcraft against Anne of Brittany to ensure Francis was the next male heir.)
Yes, sort of. She was in her mid-30s and Francis was around 18 (born 1494).
No. His mummy is not going to allow the marriage and from all accounts, she was the power behind him at this period in his life (he was into whoring and hunting, in some order). And, Anne's fertility is about to plummet. And at this point, she's more likely to die from childbirth (along with the child, given her history) than survive it. But since she died OTL in 1514, all a marriage to her does is screw up Francis' life. He's got no wife, there's no Pope Alexander to give him a dispensation to wed one of Anne's daughters (and since Claude will be Duchess, he's really screwed if he weds her mother, because that's going to her husband.....). So, no, not gonna happen.